Wrong error message «TypeError: something is not a function»

for (var i = 0; i < 18436; i++);
require('http').notAFunction();

results in

require('http').notAFunction();
^
TypeError: require is not a function

But

for (var i = 0; i < 18435; i++);
require('http').notAFunction();

results in

require('http').notAFunction();
                ^
TypeError: require(...).notAFunction is not a function

For anything ≤ 18435 the error message is correct, for anything ≥ 18436 the error message is wrong.
Reproduced on v4.x and v5.1.0. If you can't reproduce that, try using some high number there.

I can reproduce it with d8 4.6:

function func() { return {}; }
for (var i = 0; i < 18436; i++);
func().notAFunction();

% out/native/d8 test.js
test.js:3: TypeError: func is not a function
func().notAFunction();
^
TypeError: func is not a function
    at test.js:3:8

Disabling crankshaft fixes it:

% node --no-crankshaft test.js
/home/mzasso/git/chromium/v8/test.js:3
func().notAFunction();
       ^

TypeError: func(...).notAFunction is not a function

The problem is fixed in the 4.7 branch of V8.

/cc @nodejs/v8

If we can identify the fix in V8 and a it's not too complex this it seems like a good candidate for backporting all the way to v4.x.

Found it !
PR incoming ;)

deps: backport 819b40a from V8 upstream

Fix for v5.x: #3937

Fix for v4.x: #3938

This surely got a nice score in the weirdometer. Does anyone know why the breakpoint at 18435? Looking at the fix it doesn't seem like anything trivial.

The problem is that without the patch, optimized code computes the wrong message location.
I don't know why the threshold is at exactly 18436, but V8 decides to optimize the function starting from this number of iterations.

deps: backport 819b40a from V8 upstream

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Wrong error message «TypeError: something is not a function» #3934

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Wrong error message «TypeError: something is not a function» #3934

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targos commented on Nov 20, 2015

rvagg commented on Nov 20, 2015

targos commented on Nov 20, 2015

targos commented on Nov 20, 2015

targos commented on Nov 20, 2015

a0viedo commented on Nov 20, 2015

targos commented on Nov 20, 2015

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